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Subject[PATCH v2 4/4] KVM: arm64: Log source when panicking from nVHE hyp
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To aid with debugging, add details of the source of a panic. This is
done by having nVHE hyp exit to nvhe_hyp_panic_handler() rather than
directly to panic(). The handler will then add the extra details for
debugging before panicking the kernel.

If the panic was due to a BUG(), look up the metadata to log the file
and line, if available, otherwise log the kimg address that can be
looked up in vmlinux.

__hyp_panic_string is now inlined since it no longer needs to be
references as a symbol and message is free to diverge between VHE and
nVHE.

Signed-off-by: Andrew Scull <ascull@google.com>
---
arch/arm64/include/asm/kvm_mmu.h | 2 ++
arch/arm64/kernel/image-vars.h | 3 +--
arch/arm64/kvm/handle_exit.c | 31 +++++++++++++++++++++++++
arch/arm64/kvm/hyp/include/hyp/switch.h | 2 --
arch/arm64/kvm/hyp/nvhe/host.S | 17 ++++++--------
arch/arm64/kvm/hyp/nvhe/psci-relay.c | 2 --
arch/arm64/kvm/hyp/vhe/switch.c | 4 +---
7 files changed, 42 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index e52d82aeadca..f07c55f9dd1e 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -130,6 +130,8 @@ void kvm_update_va_mask(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst);
void kvm_compute_layout(void);

+#define __hyp_pa(x) ((phys_addr_t)((x)) + hyp_physvirt_offset)
+
static __always_inline unsigned long __kern_hyp_va(unsigned long v)
{
asm volatile(ALTERNATIVE_CB("and %0, %0, #1\n"
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index f676243abac6..cf12b0d6441e 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -71,8 +71,7 @@ KVM_NVHE_ALIAS(kvm_get_kimage_voffset);
KVM_NVHE_ALIAS(kvm_vgic_global_state);

/* Kernel symbols used to call panic() from nVHE hyp code (via ERET). */
-KVM_NVHE_ALIAS(__hyp_panic_string);
-KVM_NVHE_ALIAS(panic);
+KVM_NVHE_ALIAS(nvhe_hyp_panic_handler);

/* Vectors installed by hyp-init on reset HVC. */
KVM_NVHE_ALIAS(__hyp_stub_vectors);
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index cebe39f3b1b6..b25b88d8c150 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -291,3 +291,34 @@ void handle_exit_early(struct kvm_vcpu *vcpu, int exception_index)
if (exception_index == ARM_EXCEPTION_EL1_SERROR)
kvm_handle_guest_serror(vcpu, kvm_vcpu_get_esr(vcpu));
}
+
+void __noreturn __cold nvhe_hyp_panic_handler(u64 esr, u64 spsr, u64 elr,
+ u64 par, uintptr_t vcpu,
+ u64 far, u64 hpfar) {
+ u64 elr_in_kimg = __phys_to_kimg(__hyp_pa(elr));
+ u64 mode = spsr & PSR_MODE_MASK;
+
+ if (mode != PSR_MODE_EL2t && mode != PSR_MODE_EL2h) {
+ kvm_err("Invalid host exception to nVHE hyp!\n");
+ } else if (ESR_ELx_EC(esr) == ESR_ELx_EC_BRK64 &&
+ (esr & ESR_ELx_BRK64_ISS_COMMENT_MASK) == BUG_BRK_IMM) {
+ struct bug_entry *bug = find_bug(elr_in_kimg);
+ const char *file = NULL;
+ unsigned int line = 0;
+
+ /* All hyp bugs, including warnings, are treated as fatal. */
+ if (bug)
+ bug_get_file_line(bug, &file, &line);
+
+ if (file) {
+ kvm_err("nVHE hyp BUG at: %s:%u!\n", file, line);
+ } else {
+ kvm_err("nVHE hyp BUG at: %016llx!\n", elr_in_kimg);
+ }
+ } else {
+ kvm_err("nVHE hyp panic at: %016llx!\n", elr_in_kimg);
+ }
+
+ panic("HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%016lx\n",
+ spsr, elr, esr, far, hpfar, par, vcpu);
+}
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 84473574c2e7..f9e8bb97d199 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -30,8 +30,6 @@
#include <asm/processor.h>
#include <asm/thread_info.h>

-extern const char __hyp_panic_string[];
-
extern struct exception_table_entry __start___kvm_ex_table;
extern struct exception_table_entry __stop___kvm_ex_table;

diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index 3dc5a9f3e575..04d661614b0f 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -77,21 +77,18 @@ SYM_FUNC_END(__host_enter)
SYM_FUNC_START(__hyp_do_panic)
mov x29, x0

- /* Load the format string into x0 and arguments into x1-7 */
- ldr x0, =__hyp_panic_string
-
- mov x6, x3
- get_vcpu_ptr x7, x3
-
- mrs x3, esr_el2
- mrs x4, far_el2
- mrs x5, hpfar_el2
+ /* Load the panic arguments into x0-7 */
+ mrs x0, esr_el2
+ get_vcpu_ptr x4, x5
+ mrs x5, far_el2
+ mrs x6, hpfar_el2
+ mov x7, x0 // Unused argument

/* Prepare and exit to the host's panic funciton. */
mov lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
PSR_MODE_EL1h)
msr spsr_el2, lr
- ldr lr, =panic
+ ldr lr, =nvhe_hyp_panic_handler
msr elr_el2, lr

/* Enter the host, restoring the host context if it was provided. */
diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
index 8e7128cb7667..54b70189229b 100644
--- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
+++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
@@ -22,8 +22,6 @@ void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt);
struct kvm_host_psci_config __ro_after_init kvm_host_psci_config;
s64 __ro_after_init hyp_physvirt_offset;

-#define __hyp_pa(x) ((phys_addr_t)((x)) + hyp_physvirt_offset)
-
#define INVALID_CPU_ID UINT_MAX

struct psci_boot_args {
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index af8e940d0f03..7b8f7db5c1ed 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -27,8 +27,6 @@
#include <asm/processor.h>
#include <asm/thread_info.h>

-const char __hyp_panic_string[] = "HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%p\n";
-
/* VHE specific context */
DEFINE_PER_CPU(struct kvm_host_data, kvm_host_data);
DEFINE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
@@ -207,7 +205,7 @@ static void __hyp_call_panic(u64 spsr, u64 elr, u64 par)
__deactivate_traps(vcpu);
sysreg_restore_host_state_vhe(host_ctxt);

- panic(__hyp_panic_string,
+ panic("HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%p\n",
spsr, elr,
read_sysreg_el2(SYS_ESR), read_sysreg_el2(SYS_FAR),
read_sysreg(hpfar_el2), par, vcpu);
--
2.30.0.617.g56c4b15f3c-goog
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